I’d love to see an animated version of this. It’s a maximal outburst flood from Glacial Lake Missoula modeled by Roger Denlinger and Daniel O’Connell. I wrote about their work in 2010:
During the last ice age, a continent-spanning ice sheet built from massively expanded glaciers descended from the Canadian Rocky Mountains to reach deep into Washington, Idaho and Montana. Glacial Lake Missoula formed behind a miles-long dam of ice across what is now the valley of the Clark Fork and Pend Oreille rivers running from Montana to northeast Washington. The dam formed and collapsed dozens of times over a span of three thousand years.
In the simulation of one of the largest possible floods, raging water quickly overwhelms the hills near Spokane and races overland to the south and west. The intense, overland flows carve the miles-long scars of the scablands between Spokane and Pasco, Wash.
Thirty-eight hours later, swirling, mud-darkened waters converge at the narrowing of the Columbia at Wallula Gap, where the backed-up flow rises 850 feet above river level (1,150 feet above sea level). An immense volume of water blasts through the narrows at fire-hose velocity. Flow exceeds 1.3 billion gallons per second — a thousand times greater than the Columbia’s average flows today.
Lake Missoula’s water, all 550 cubic miles of it, drains in 55 hours — less than three days — according to the model. At that time, the flood surge peaks in the Columbia Gorge at The Dalles, rising 950 feet above river level (1,000 feet above sea level), spilling over the gorge walls in places, and flooding the valleys of tributaries for miles upstream.
Inundation of the Willamette Valley peaks on the seventh day after dam burst, in the simulation. Flooding reaches as far south as Eugene. Loaded with mud and gravel, the flood dumps sediment across the entire valley.
Such a vast inundation, far greater than anything ever witnessed in historical time, seemed impossible to geologists in the 1920s, when J Harlen Bretz proposed that the scablands resulted from a catastrophic flood, not eons of gradual erosion. The idea didn’t gain mainstream acceptance until the 1960s. [Continue reading]